In the Third Generation Partnership Project (3GPP), the fourth generation (4G) cellular network includes an evolved packet system (EPS). The EPS may include a radio access network (e.g., referred to as a long term evolution (LTE) network), a wireless core network (e.g., referred to as an evolved packet core (EPC) network), an Internet protocol (IP) multimedia subsystem (IMS) network, and a packet data network (PDN). The LTE network is often called an evolved universal terrestrial radio access network (E-UTRAN). The EPC network is an all-IP packet-switched core network that supports high-speed wireless and wireline broadband access technologies. The EPC network allows user equipment (UEs) to access various services by connecting to the LTE network, an evolved high rate packet data (eHRPD) radio access network (RAN), and/or a wireless local area network (WLAN) RAN. The IMS network may include an architectural framework or network (e.g., a telecommunications network) for delivering IP multimedia services. The PDN may include a communications network that is based on packet switching.
Voice-over-LTE (VoLTE) is a service provided by the LTE network and is based on the IMS network. VoLTE provides specific profiles for control and media planes of a voice service on the LTE network. VoLTE delivers the voice service (e.g., the control and media planes) as data flows within a LTE data bearer. Therefore, VoLTE does not depend on and eliminates a need for a legacy circuit-switched voice network.